Kantronics KPC–3 Plus User Manual page 214

A 0.1 F capacitor (non-polarized) usually is required in the transmit audio
line from the TNC to any handheld transceiver (HT) radio. Even if a capacitor
is not required for connection to a particular radio, it can still be installed, and
the transmit audio (packets) will pass through to the radio.
ICOM HT radios key the PTT by providing a low impedance path from the mic
input to ground. To accomplish this, simply install a resistor (approximately
3.9 kΩ seems to be a good value) in series with the PTT wire from the KPC-3
Plus, and connect this to the mic input along with the AFSK line.
The ICOM 2A style wiring is most common, and can be used with some
Alinco, Azden, and standard HTs.
YAESU radios are similar but use a mono plug and a different value resistor.
The wiring for Yaesu HTs can also be used with Radio Shack HTs.
Most KENWOOD HT radios key the PTT line by connecting the sleeve of the
mic connector to the sleeve of the earpiece connector. This means that you
will not need a resistor in the PTT wire from the KPC-3 Plus, simply connect
the PTT wire to the sleeve of the mic connector. Another point to watch: most
of the KENWOOD HTs (2600 and later) use a three pin mic connector. The
AFSK from the KPC-3 Plus should therefore connect to the RING and not the
TIP of the mic connector.
Leave J9 in normal (not HT) when using Kenwood HTs.
Optional Connections to DSUB-9 Radio Port
Pin 7 of the DSUB-9 connector may be configured to allow you to apply power to, or to
perform a soft reset on, your KPC-3 Plus.
Applying Power through the DSUB-9 connector.
To power the KPC-3 Plus from Pin 7 of the DSUB-9 connector, you must connect J7
center pin and pin 2, J6 center pin and pin 2.
Resetting the KPC-3 Plus through the DSUB-9 connector.
To perform a soft reset from Pin 7 of the DSUB-9 connector, you must connect J7
center pin and pin 2, J6 center pin and pin 1. Momentarily applying a ground to pin 7 will
then perform a soft reset.
Alternatively, pin 9 can be used for either ground or reset with jumper J5: Connect J5
center pin and pin 1 for ground, center pin and pin 2 for external reset.
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